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    <title>Document</title>
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    <!-- 
        if-- else if --else
    -->
    <script>
        /* age>=18 成人
        6<=age<=18 青少年
        age<6   儿童 */
        var age=5;
        if(age>=18){
            console.log("成人")
        }else if(age>=6){
            console.log("青少年")
        }else {
            console.log("儿童")
        }
        </script>
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